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 ###Instrução: Qual é a potência do sinal para JOAB-DTV?
 ###Tabelas: CREATE TABLE populations (populations_id AUTO_INCREMENT PRIMARY KEY, Country VARCHAR, Orphans as % of all Children INT, AIDS Orphans as % of Orphans INT, Total Orphans (Total) INT, Total Orphans (AIDS Related) VARCHAR, Maternal (Total) INT, Maternal (AIDS Related) VARCHAR, Paternal (Total) INT, Paternal (AIDS Related) VARCHAR, Double (Total) INT, Double (AIDS Related) VARCHAR) CREATE TABLE ethnic_groups_and_demographics (ethnic_groups_and_demographics_id AUTO_INCREMENT PRIMARY KEY, Raion (district) or City VARCHAR, Total VARCHAR, Ukrainians VARCHAR, Moldovans VARCHAR, Bessarabian Bulgarians VARCHAR, Russians VARCHAR, Gagauzians VARCHAR, Other ethnic groups² VARCHAR) CREATE TABLE television_broadcasters (television_broadcasters_id AUTO_INCREMENT PRIMARY KEY, Channel INT, Channel name VARCHAR, Callsign VARCHAR, Signal power VARCHAR, Broadcast area VARCHAR) CREATE TABLE m (m_id AUTO_INCREMENT PRIMARY KEY, Township VARCHAR, County VARCHAR, Pop. (2010) INT, Land ( sqmi ) VARCHAR, Water (sqmi) VARCHAR, Latitude VARCHAR, Longitude VARCHAR, GEO ID INT, ANSI code INT) CREATE TABLE 2011_season (2011_season_id AUTO_INCREMENT PRIMARY KEY, Week INT, Date VARCHAR, Visiting Team VARCHAR, Final Score VARCHAR, Host Team VARCHAR, Stadium VARCHAR)  
SELECT Signal power FROM television_broadcasters WHERE Callsign = JOAB-DTV